1. Field of the Invention
The present invention generally relates to a robotic apparatus and, more particularly, to a robotic apparatus adapted to travel through enclosed spaces such as conduits or ducts using mechanically enabled helical-like motions.
2. Background of Relevant Art
Pipe crawlers, pipe inspection pigs and similar vehicles are widely used for inspecting the interior surfaces of piping systems, storage tanks, and process vessels for damaged or flawed structural features. Typically, such devices include a testing probe, sensor, or camera carried by a support structure that travels through the piping system being inspected.
Many of the remote inspection devices have been designed for pipes having a six-inch or greater inner diameter. However, there remains a need for the inspection of smaller diameter pipes, such as coiled steel tubing. In particular, there is a need for small-diameter inspection devices that are capable of travelling very long distances. For example, coiled steel tubing is often produced with lengths of 7,620 m (25,000 ft) at 32 mm (1.25 in) diameter or 1,800 m (6,000 ft) at 90 mm (3.5 in) diameter. Lengths of coiled tubing are stored on reels with diameters from 2 ft to 20 ft.
While current advances in miniaturization technology have made cameras and sensors small enough to fit within a small diameter pipe, there have been few advances in the design of a crawling apparatus having adequate motive forces to deploy a small diameter inspection apparatus through an extensive pipe system. For example, miniature electric motors do not provide enough motive force to pull extensive length tethers behind the crawler. Similarly, miniature air cylinders do not have the capacity to generate enough pushing force directly against the inner-walled pipe as is required for inch-worm motion. In addition, neither technology is capable of propelling an inspection devices of the mile-plus distances that may be required.
The art teaches a variety of larger-diameter pipe inspection apparatuses. One such apparatus is taught in U.S. Pat. No. 4,006,359 to Sullins et al. The crawler of Sullins et al. is a completely self-contained, self-propelled and self-operated vehicle adapted to travel through a pipeline, stop at particular locations such as a girth weld between adjoining sections of pipe, inspect the weld, for example by X-raying it and then proceed onto the next location to be inspected. While suitable for use in large diameter pipelines and traveling short distances, the crawler of Sullins et al. would not be feasible for use in coiled tubing for the following reasons. First, Sullins et al's crawler includes x-ray equipment (e.g. x-ray tube), which has not yet been fabricated to fit in small pipe diameters. Secondly, because x-ray equipment requires a large amount of power to operate, the size of the power source is dependent on the x-ray equipment, and thus greatly increased. Therefore, in addition to the x-ray equipment, the size of the power source may prohibit the crawler from traveling in small diameter spaces for long distances.
Another such apparatus is taught in U.S. Pat. No. 5,392,715 to Pelrine. Pelrine teaches an in-pipe running robot which does not easily turn over even when running round circumferentially inside piping. Still another such apparatus is taught in U.S. Pat. No. 4,862,808 to Hedgcoxe et al. Hedgcoxe et al. describes a robotic pipe crawling device having module pivot flexibility, which enables the device to negotiate corners with complete autonomy. However, there are limitations to the size and motive force capable of being exerted by these prior art devices as set forth above.
In particular, there is a need for a pipe inspection apparatus that will provide the necessary motive force for small diameter pipes. The apparatus should be dimensioned to pass through various sizes of piping and be able to readily negotiate bends in the piping. In addition, the pipe crawler should be autonomous and able to generate a sufficient motive force that can propel inspection equipment. Also, the pipe crawler should be capable of traveling in forward and backward directions, accelerating, decelerating, and stopping.
Thus, what is needed is a robotic apparatus that overcomes the deficiencies of the currently available technologies.